Nolpitantium besilate

The neurokinin‐1 receptor (NK‐1R) antagonists are approved as treatment for chemotherapy‐associated nausea and vomiting in cancer patients. The emerging role of the substance P‐NK‐1R system in oncogenesis raises the possibility of repurposing well‐tolerated NK‐1R antagonists for cancer treatment. This study reports that human colorectal cancer (CRC) patients with high NK‐1R expression have poor survival, and NK‐1R antagonists SR140333 and aprepitant induce apoptotic cell death in CRC cells and inhibit CRC xenograft growth. This cytotoxicity induced by treatment with NK‐1R antagonists is mediated by induction of endoplasmic reticulum (ER) stress. ER stress triggers calcium release, resulting in the suppression of prosurvival extracellular signal‐regulated kinase (ERK)‐c‐Myc signaling. Along with ER calcium release, one ER stress pathway mediated by protein kinase RNA‐like ER kinase (PERK) is specifically activated, leading to increased expression of proapoptotic C/EBP‐homologous protein (CHOP). Moreover, NK‐1R antagonists enhance the efficacy of chemotherapy by increasing the sensitivity and overcoming resistance to 5‐fluorouracil in CRC cells through the induction of sustained ER stress and the consequent suppression of ERK‐c‐Myc signaling both in vitro and in vivo. Collectively, the findings provide novel mechanistic insights into the efficacy of NK‐1R antagonists either as a single agent or in combination with chemotherapy for cancer treatment.

Substance P (SP) regulates inhibitory synaptic transmission mediated by GABA_A receptors in the cerebral cortex; however, SP-mediated regulation of excitatory synaptic transmission remains poorly understood. We performed whole-cell patch-clamp recordings from pyramidal neurons to examine the effects of SP on excitatory postsynaptic currents (EPSCs) mediated via AMPA receptors in the insular cortex (IC), which is involved in nociceptive information processing. First, EPSCs evoked by minimal electrical stimulation (eEPSCs) including stepwise EPSCs and failure events, were examined. SP dose-dependently suppressed mean eEPSC amplitude, partially due to an increase in the failure rate of eEPSCs. The SP-induced suppression of eEPSCs was accompanied by an increase in the paired-pulse ratio and was inhibited by the preapplication of SR140333, an NK1 receptor antagonist. [Sar⁹,Met(O₂)¹¹]-substance P, an NK1 receptor-selective agonist, mimicked the effects of SP on eEPSCs and decreased the frequency of miniature EPSCs (mEPSCs) without changing the average mEPSC amplitude. Considering that most NK1 receptors in the cerebral cortex are expressed in nitric oxide synthase (NOS)-positive GABAergic neurons, the SP-induced suppressive effect on EPSCs may be mediated by nitric oxide (NO) in this subtype of GABAergic neurons. NO imaging using the fluorescent probe DAX-J2 Red supports this hypothesis: SP increased the fluorescence intensity of DAX-J2 Red in some GABAergic neurons. Furthermore, both L-NAME, an NOS inhibitor, and PTIO, an NO scavenger, diminished the SP-induced suppression of eEPSCs. These results suggest that the activation of presynaptic NK1 receptors contributes to SP-induced eEPSC suppression by activating the NO synthesis pathway in GABAergic neurons. (246 words).